[egenix-users] mx.odbc segmentation fault on fetching string

[M.-A. Lemburg]

On 2008-06-03 02:49, Wouter van Atteveldt wrote:
> Dear list,
> 
> I am evaluating mx.odbc for connecting to a MS SQL server from my Linux machine using freetds 0.82. I can connect and query using isql without problem, but I get a segmentation fault if I fetch using the mx.odbc interface.

isql uses a different, all-strings based access method to the ODBC
driver, so it can really only be used to verify that a connection
works, not much more.

mxODBC always tries to use the best possible access method to
avoid frequent copying and conversion of the data.

> wva at amcat:~/tmp$ isql -v AmcatDB <UID> <PWD>
> +---------------------------------------+
> | Connected!
> [...]
> +---------------------------------------+
> SQL> select top 1 projectid, name from projects
> [...]
> | 1          | test
> [...]
> SQLRowCount returns 1
> 1 rows fetched
> 
> wva at amcat:~/tmp$ python testodbc.py
> connected to Microsoft SQL Server 08.00.2039
> Executed, fetching...
> [(1,)]
> Executed, fetching...
> Segmentation fault

Could you send us the core dump of this segfault ? It is most likely
a problem in the new FreeTDS ODBC driver. FreeTDS 0.63 works just fine
on x64 machines.

It would be great if you could also provide the table
definition and example data that allows us reproducing the
error on our servers.

> wva at amcat:~/tmp$ cat testodbc.py
> import mx.ODBC
> db = mx.ODBC.unixODBC.connect("AmcatDB", "<UID>", "<PWD>")
> print "connected to %s %s" % (db.dbms_name, db.dbms_version)
> c = db.cursor()
> c.executedirect("select top 1 projectid from projects")
> print "Executed, fetching..."
> print c.fetchall()
> c.executedirect("select top 1 projectid, name from projects")
> print "Executed, fetching..."
> 
> print c.fetchall()wva at amcat:~/tmp$ uname -a
> Linux amcat 2.6.18-6-amd64 #1 SMP Sun Feb 10 17:50:19 UTC 2008 x86_64
> GNU/Linux
> wva at amcat:~/tmp$ python -c "import sys;print(sys.maxunicode<66000)and'UCS2'or'UCS4'"
> UCS4
> 
> As you can see, it returns the MS SQL version number so it has some contact with the remote db. I installed using egenix-mxodbc-3.0.1.linux-x86_64-py2.5_ucs4.prebuilt.zip, which I think should be OK as x86_64 == AMD64 (right?). projected is int, name is a varchar(255) column, and the table should have a couple hundred entries at most.
> 
> The relevant etc files:
> 
> wva at amcat:~/tmp$ tail -4 /usr/local/freetds/etc/freetds.conf
> [amcatdb]
>         host = localhost
>         port = 1433
>         tds version = 8.0
> wva at amcat:~/tmp$ cat /etc/odbc.ini
> [AmcatDB]
> Driver          = FreeTDS
> Description             = amcatdb MS SQL Database
> Trace           = No
> Servername              = amcatdb
> Database                = anoko
> wva at amcat:~/tmp$ cat /etc/odbcinst.ini
> [FreeTDS]
> Description             = v0.63 with protocol v8.0
> Driver          = /usr/local/freetds/lib/libtdsodbc.so
> UsageCount              = 1
> 
> Note that I am using an SSH tunnel to connect to the sql server, hence the localhost. This does not give trouble using either tsql, isql, or python-sybase (on a previous install), so I am not expecting this to be the cause of the problem.
> 
> Any help greatly appreciated!

Thanks,
-- 
Marc-Andre Lemburg
eGenix.com

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